BOM: El Niño likely past its peak

A number of El Niño-Southern Oscillation (ENSO) indicators suggest that the 2015-16 El Niño has peaked in recent weeks. Tropical Pacific Ocean temperatures suggest this event is one of the top three strongest El Niño events of the past 50 years. Climate models suggest the 2015-16 El Niño will decline during the coming months, with a return to ENSO neutral likely during the second quarter of 2016.

In the central to eastern tropical Pacific Ocean, the sea surface and sub-surface have cooled in recent weeks, though temperatures remain at strong El Niño levels. In the atmosphere, the Southern Oscillation Index has eased to weak El Niño values. Recent bursts of westerly winds over the equatorial western Pacific may temporarily slow the decline of El Niño.

Based on the 26 El Niño events since 1900, around 50% have been followed by a neutral year, while 40% have been followed by La Niña. Models also suggest neutral and La Niña are equally likely for the second half of 2016, with a repeat El Niño the least likely outcome. Historically, the breakdown of strong El Niño events brings above average rainfall to parts of Australia in the first half of the year.

The Indian Ocean Dipole has little influence on Australian climate between December and April. However, Indian Ocean sea surface temperatures remain very much warmer than average across the majority of the basin. This basin-wide warmth may provide extra moisture for rain systems across Australia.

Indian Ocean Dipole

The Indian Ocean Dipole (IOD) is neutral. The index value to 3 January was -0.36 °C.

Sea surface temperatures (SSTs) remain significantly warmer than average across most of the Indian Ocean basin.

The influence of the IOD on Australian climate is weak during the months December to May as the monsoon trough shifts south over the tropical Indian Ocean. However, widespread record-warm sea surface temperatures in the Indian Ocean are likely to influence Australian climate during the summer months. These warm waters act as a source of moisture, and may provide extra moisture for rainfall systems developing over Australia.